Characterization of Human Lymphocytes Bearing Fc Receptors for IgE Isolated from Blood and Lymphoid Organs

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Abstract
Human lymphocytes isolated from adult peripheral blood and cord blood, tonsils, adenoids and spleens were analysed for Fc receptors for IgE (FcE) by rosette assays. The FcE+ cells were also characterized for their class of surface immunoglobulin (sIg), complement receptors, receptors for sheep erythrocytes (E), and Helix pomatia A haemagglutinin (HP), and their abilities to phagocytoze and adhere. The average number of FcE+ cells was in adult peripheral blood 1.2±0.4%, in cord blood 3.0±1.3%, in tonsils 4.2±5.2%, in adenoids 5.8±4.2%, and in spleens varied from 0.8% to 15.8% among individual patients. Overnight culturing of the lymphocytes under conditions that allowed detection of Fc receptors for IgM (Fcμ) usually lowered the number of FcE+ cells. Neuraminidase treatment caused no change. Rosette formation was inhibited by IgE myeloma proteins and their Fc fragments, but not by mildly reduced and alkylated and heated (56°C) IgE, indicating that the receptors are specific for the native configuration of the IgE Fc fragment. Double cell surface marker analyses with fluoresceinated F(ab')2 fragments of purified anti‐μ, δ, and γ antibodies used to label the FcE rosette‐forming lymphocytes from peripheral adult and cord blood showed that 50–80% were sIgM+ but only 0–28% were sIgD+. In contrast, approximately 80% of the FcE+ cells from tonsils, adenoids and spleens were sIgM+ and sIgD+. The FcE+ lymphocytes represented 10–20% of the sIgM+ lymphocytes in both the peripheral adult and cord blood. Depletion and enrichment experiments indicated that most of the FcE+ cells bear complement receptors. Lymphocytes having both E and FcE receptors were not found. Furthermore, the lymphocytes with HP receptors, a marker for T cells and immature B cells, were FcE−. Monocytes and neutrophil granulocytes did not form FcE rosettes. These data indicate that a minor population of human B lymphocytes have FcE receptors. The majority of the FcE+ lymphocytes in the blood differ from those in tonsils, adenoids and spleen in that the majority of the former are sIgM+/sIgD− and the latter sIgM+/sIgD+. The sIgM+/sIgD− FcE+ cells in the blood are probably relatively mature lymphocytes since they lacked HP receptors, which are found on immature B cells